I had a dentist appointment (not the first time with this dentist) during which he voluntarily did a gum prob. Two weeks after that I had classical flu
symptoms ( i did get the flu shot). The fever last for a week, but the symptoms persisted for 4 more weeks.
I have seen the dentist not maintaining basic hygiene protocols , like changing gloves between patients before (sometimes, not regularly). I haven't paid attention then, as he was someone i could afford within my budget.